Computer networks such as the Internet are driving increased acceptance of personal computers. Network communication began with text-only e-mail and file-transfer protocols (FTP), but with improved user interfaces and graphics, graphical browsing has become commonplace. Mission-critical business transactions, corporate database queries, and even video conferencing and voice telephone calls all use the Internet.
Not surprisingly, the Internet and local networks are becoming crowded. Simply increasing bandwidth is expensive and often only shifts bottlenecks to another part of the network. While users may not notice delayed e-mail, Internet browsing can become painfully slow during times of network congestion. Video conferencing and telephony suffer poor quality and even gaps of lost speech when the network is slow.
FIG. 1 illustrates differing priorities of various kinds of network traffic. Two-way video and audio communications such as video conferencing and Internet telephony must have their packets delivered over the network in real time, or parts of the conversation are lost. Thus these services must have the highest priority in most networks. Business-critical applications such as financial transactions and accesses of corporate databases have moderately high priority. Browser traffic to the world-wide-web has a lower priority since much of this traffic is for information gathering and personal uses. However, browser traffic should not be so slow as to irritate the users. Lowest in priority are file transfers and e-mail, since these are usually not needed immediately.
Server traffic tends to have a higher priority than client traffic, since business-critical applications reside on corporate servers. Clients are usually individual desktop PC's.